Hi Michael,
On Wed, Apr 03, 2013 at 11:17:58AM +0200, Michael Kerrisk wrote:
> Hello Minchan,
>
> On Mon, Mar 25, 2013 at 7:21 AM, Minchan Kim <minchan@xxxxxxxxxx> wrote:
> > These day, there are many platforms avaiable in the embedded market
> > and they are smarter than kernel which has very limited information
> > about working set so they want to involve memory management more heavily
> > like android's lowmemory killer and ashmem or recent many lowmemory
> > notifier(there was several trial for various company NOKIA, SAMSUNG,
> > Linaro, Google ChromeOS, Redhat).
> >
> > One of the simple imagine scenario about userspace's intelligence is that
> > platform can manage tasks as forground and backgroud so it would be
> > better to reclaim background's task pages for end-user's *responsibility*
> > although it has frequent referenced pages.
> >
> > This patch adds new knob "reclaim under proc/<pid>/" so task manager
> > can reclaim any target process anytime, anywhere. It could give another
> > method to platform for using memory efficiently.
> >
> > It can avoid process killing for getting free memory, which was really
> > terrible experience because I lost my best score of game I had ever
> > after I switch the phone call while I enjoyed the game.
> >
> > Writing 1 to /proc/pid/reclaim reclaims only file pages.
> > Writing 2 to /proc/pid/reclaim reclaims only anonymous pages.
> > Writing 3 to /proc/pid/reclaim reclaims all pages from target process.
> >
> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> > ---
> > fs/proc/base.c | 3 ++
> > fs/proc/internal.h | 1 +
> > fs/proc/task_mmu.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/rmap.h | 4 ++
> > mm/Kconfig | 13 ++++++
> > mm/internal.h | 7 +---
> > mm/vmscan.c | 59 ++++++++++++++++++++++++++
> > 7 files changed, 196 insertions(+), 6 deletions(-)
> >
> > diff --git a/fs/proc/base.c b/fs/proc/base.c
> > index 9b43ff77..ed83e85 100644
>
> [...]
>
> > +#define RECLAIM_FILE (1 << 0)
> > +#define RECLAIM_ANON (1 << 1)
> > +#define RECLAIM_ALL (RECLAIM_FILE | RECLAIM_ANON)
> > +
> > +static ssize_t reclaim_write(struct file *file, const char __user *buf,
> > + size_t count, loff_t *ppos)
> > +{
> > + struct task_struct *task;
> > + char buffer[PROC_NUMBUF];
> > + struct mm_struct *mm;
> > + struct vm_area_struct *vma;
> > + int type;
> > + int rv;
> > +
> > + memset(buffer, 0, sizeof(buffer));
> > + if (count > sizeof(buffer) - 1)
> > + count = sizeof(buffer) - 1;
> > + if (copy_from_user(buffer, buf, count))
> > + return -EFAULT;
> > + rv = kstrtoint(strstrip(buffer), 10, &type);
> > + if (rv < 0)
> > + return rv
> > + if (type < RECLAIM_ALL || type > RECLAIM_FILE)
> > + return -EINVAL;> + task = get_proc_task(file->f_path.dentry->d_inode);
>
> The check here is the wrong way round. Should be
>
> if (type < RECLAIM_FILE || type > RECLAIM_ALL)
>
> Thanks,
You give me a chance to remember "last minute change is really evil"
Thanks!
--
Kind regards,
Minchan Kim
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